“EPFL Outstanding Ph.D Thesis Distinction in Civil and Environmental Engineering” 2020
Ph.D in the Computational Solid Mechanics Laboratory, LSMS
Thesis title: Bridging scales in Wear Modeling with Volume Integral Methods for Elastic-Plastic Contact
Friction and wear are fundamental tribological phenomena that affect many aspects of our society: from the gears of a Swiss watch to car brakes and earthquakes. Despite being integral parts of everyday life, friction and wear remain elusive to quantitative predictions. Their systematic study, since the seminal experiments of Da Vinci, Amontons and Coulomb, has been quasi-exclusively experimental. This limits our capacity to understand tribological systems to those that can be reproduced experimentally. Perhaps the most challenging factors are the profoundly multi-scale and multi-physics aspect of both friction and wear, as well as the difficulty of observing what occurs at frictional interfaces.
Due to natural or artificial roughness, things that appear in contact at the macro-scale actually only interact on an area that is much smaller than their apparent contact area. The processes that give rise to macroscopic friction and wear occur that the micro-contacts that make up this “true” contact area. During my thesis, I have developed simulation methods to accurately compute contact interfaces with multi-scale roughness. Because the true contact area is small, contact pressures can be very large, causing plastic (irreversible) deformation of the bodies in contact. To account for this effect, I developed a new approach to volume integral methods. My contributions allowed large scale simulations of plastic rough contact, which contributed to the understanding of the role of plasticity on the formation of cracks that can lead to wear debris detachment.
As a postdoctoral fellow at Johns Hopkins University in Baltimore, I study the micro-scale friction mechanisms of self-assembled monolayers and the wear of polymer systems.
Ph.D in the the Laboratory of Ecological Systems, ECOS
Thesis title: Alternative land use change scenarios for the expansion of a
more sustainable agriculture in the tropics.
Expansion of oil palm plantations in the tropics, particularly in Southeast Asian countries, has been blamed for unprecedented rates of deforestation in recent decades. The continuing expansion of oil palm agriculture across tropical countries poses significant threats and pressure to ecosystems and potentially the global climate. Along my PhD work, I assessed the impacts of alternative pathways for a more sustainable development of oil palm agriculture with a focus on carbon and soil biogeochemistry.
In general, expansion of oil palm in Latin-America has not been at high deforestation cost because land previously cleared for other agricultural uses has often been used. Based on a long-term chronosequence in Colombia encompassing two-cycle plantations (over 56 years) on former pastures areas, I demonstrated that oil palm cultivation can be carbon neutral from an ecosystem standpoint (considering both the development of the plant biomass and the soil organic matter). I also found that a second investigated deforestation-free land use change scenario, converting savanna into oil palm, led to a positive ecosystem carbon balance. In parallel with these two positive ecosystem carbon outcomes at the ecosystem level, other important soil biogeochemical characteristics, i.e. soil biological activity, showed promising trends for the sustainability of oil palm agroecosystems if more ecologically oriented management practices are adopted, in particular in promoting organic inputs.
It is concluded that for a pathway toward sustainability in the eminent expansion scenario of oil palm plantations, emphasis should be put on degraded pastures or degraded savannas if they cannot be restored. Currently, as a post-doctoral fellow at ETH, I am integrating and synthetizing the data and insights produced by research groups of a wide range of expertise in natural science in the frame of the Oil Palm Adaptive Landscapes (OPAL) project.
Thesis title: Measurement-system design for structural identification
Ph.D. in the Applied Computing and Mechanics Laboratory (IMAC) and Future Cities Laboratory, Singapore-ETH Centre.
The management of existing civil infrastructure is challenging due to evolving function requirements, aging and climate change. Civil infrastructure often has hidden reserve capacity because of the conservative approaches used in construction design and practice. The information collected through sensor measurements has the potential to improve knowledge of the structural behavior, such as the maximal load-bearing capacity of a bridge. In this situation, the design of the monitoring system is crucial as the information collected during load testing depends on this choice. However, this task is usually carried out by engineers using only qualitative rules of thumb and experience, limiting the information gain on structural behavior during monitoring.
The aim of the thesis was to develop algorithms to design measurement systems. New methods have been presented in order to either maximize the information gain of a sensor configuration or recommend an optimal solution based on multiple conflicting performance criteria. Additionally, a methodology has been introduced to assess whether monitoring information can influence decisions on asset management. Results on three full-scale bridges and one excavation site have shown that an optimal measurement-system design leads to better understandings of the structural behavior.
As a post-doctoral fellow at EPFL in the Laboratory for Maintenance and Safety of Structures (MCS), I am currently working on new diagnostic tools and innovative maintenance strategies to retrofit damaged bridges.
“EPFL Outstanding Ph.D Thesis Distinction in Civil and Environmental Engineering” 2019
Thesis title: When dynamic cracks meet disorder: A journey along the fracture process zone
Ph.D in the Computational Solid Mechanics Laboratory, LSMS
My PhD research focused on the rapid propagation of rupture front, a highly dynamic phenomenon at the origin of many catastrophic events. In the wake of a dynamic rupture, materials and structures fail, violent earthquakes nucleate along crustal faults, snow avalanches start hurtling down steep mountain slopes, drops of delicious wine spill out of a breaking glass. In each of these examples, the medium holds inherent heterogeneities (defects, inclusions, microstructure) which are magnified by the sharp stress concentration existing at the tip of the front. Understanding their impact on the rupture dynamics is hence a fundamental but challenging problem.
During my thesis at the Computational Solid Mechanics Laboratory (LSMS), I developed and used high-performance numerical methods to simulate the propagation of dynamic ruptures within heterogeneous materials. The developed models allowed to challenge the predictions of the dynamic fracture theory in the presence of microscopic heterogeneities. In a second phase, the same framework was applied to study the onset of sliding along frictional interfaces. In the context of friction, the microscopic heterogeneity stems from the sparse contact points existing when two rough surfaces come into contact. The obtained results shed new light on the dynamics of seismic ruptures and the energy budget of earthquakes.
As a post-doctoral fellow at the University of Oslo, I am currently studying how earthquake ruptures interplay with fluid present in the Earth crust, notably in the context of seismicity induced by underground fluid injection.
Thesis title: Two-dimensional crack growth in FRP structures
Ph.D in Composite Construction Laboratory, CCLAB
Fiber-reinforced polymer (FRP) composite materials are currently being selected for the design of lightweight and efficient structural members in a wide number of engineering applications. The load-bearing capacity of FRP structures can be significantly reduced by delamination and debonding damage which, in actual structural members, may extend all around its perimeter, thus constantly changing the size of the crack front. However, most research efforts concerning the fracture characterization of delamination and debonding damage have focused on one‑dimensional (1D) fracture specimens where cracks propagate longitudinally with an approximately constant crack width, thus resulting in fracture properties that may lead to inaccurate predictions of fracture behavior in real structures. The aim of my thesis was thus to investigate, characterize and quantify, experimentally and numerically, potential 2D effects on the 2D delamination in laminates and 2D debonding in face sheet/core interfaces of sandwich structures that are not captured by 1D fracture mechanics tests. The thesis developed the scientific bases for a better understanding of delamination and debonding in real 2D cases.
Currently I am working as a project engineer for Ingeni SA in Geneva, a cutting-edge structural engineering office with four offices in Switzerland.
“EPFL Outstanding Ph.D Thesis Distinction in Civil and Environmental Engineering” 2018
Thesis title: Extreme Hydrodynamic impact onto buildings
Ph.d in the Laboratory of Hydraulic Constructions
Thesis title: Ecohydrological and Metacommunity Studies of Proliferative Kidney Disease Spread in Freshwater Salmonid Fish
Ph.D in the Laboratory of Ecohydrology, ECHO
My Ph.D. research focuses on on-demand mobility services. In the first years of my Ph.D., I developed knowledge about the effects of such services in traffic conditions of an urban area. To date, our simulations enlightened the impacts that the number of available drivers and the passengers’ attitude towards shared-ride options has on congestion. It was possible to show how service providers can attract drivers to decrease waiting times faced by passengers at the expense of deteriorating average traveling speeds for everyone in the city.
The Laboratory for Innovative Mobility Systems (LIMOS), led by Prof. Yafeng Yin at the University of Michigan, has contributed to the literature of emerging transportation technologies during the last 20 years. For my academic visit to LIMOS, I aim to develop policies on innovative on-demand transportation modes capable of improving the welfare of society with a sustainable outcome for all stakeholders, mitigating negative externalities. Overall, the experience obtained there will allow me to expand my research to a more comprehensive side of mobility problems.
After joining Transport and Mobility Laboratory (TRANSP-OR) in September 2018, I have started working on demand-based operations of vehicle sharing systems (VSS). In the first stage of my PhD thesis, we have conducted an extended literature review and proposed a holistic framework that identifies the relations between different decision levels, different actors, and different layers. As an outcome of the framework, we have seen that there is more focus on supply aspects than demand aspects in the literature. One of the main issues for this skew is because the disaggregate data collection and developing a demand model are exhaustive and costly.
To address this issue, we have decided to use the Multi-Agent Transport Simulation (MATSim). The main idea is to utilize MATSim as a ground truth and analyze different configurations and their relations to rebalancing operations. Assist. Prof. Joseph Chow, from the C2SMART lab in New York University (NYU) Tandon School of Engineering, and his team have been working on the rebalancing strategies for car sharing services using MATSim. His expertise on this topic will contribute developing a more structured framework according to the advantages and limitations of MATSim.
As part of the Structural Xploration Lab (SXL), I work at the interface between architecture and structural engineering with the aim of exploring the design space of structurally-aware structures. My research mainly focuses on the development of a novel design computational workflow that generates reticulated structures in static equilibrium at an early design stage, as a result of user defined force-driven rules rather than numerical variables. Its implementation is reflected on a user-controlled, form-finding engine which unveils unprecedent structural typologies through the extensive exploration of the design space. Part of the research objectives is the human-machine collaboration and the exploitation of intelligence and logic sourcing from both sides.
During my academic visit to the “Digital Structures” research lab of Prof. Caitlin Muller, at the Massachusetts Institute of Technology (MIT), I aim to integrate artificial intelligence into the developed computational workflow. This approach will upgrade the machine as a collaborative partner during the design process, that contributes with its own intelligence towards the final design. Overall, the guidance and experience gained there will allow me extend my research towards a more intelligent and multidisciplinary approach.
In the scope of my PhD research project ‘’Composite sandwich bridge decks on fire’’, I investigate the thermo-mechanical behavior of composite sandwich bridge decks composed of glass fiber-reinforced (GFRP) face sheets and a balsa wood core during a fire. This new type of sandwich bridge decks has to meet the same requirements as traditional decks do. In particular, their behavior during a fire incident has to be known and predictable.
As a main step of my project, numerical thermo-physical and thermo-mechanical sandwich response models are currently developed and will be validated by the fire resistance experiments. The mentioned fire resistance experiments are my mobility project that will be performed on full-scale GFRP-Balsa sandwich panels and require a specific instrumentation. All the equipment’s will be provided by CERIS (Civil Engineering Research and Innovation for Sustainability) of the Instituto Superior Técnico (IST), during a totally six months stay at the beginning of next year.
I enrolled in the doctoral program of EDCE, EPFL and started my Ph.D at the Laboratory for Timber Constructions (IBOIS) in July 2016. My research is mainly focused on the mechanical characterization and structural optimization of spatial timber-plate structures using wood-wood connections, for which multiple experimental investigations have been already carried out. In parallel, I have recently introduced and developed a new modeling strategy for timber plate structures. The strategy, which is referred to as “macro models”, aims to simulate the global behavior of timber plate structures, reduce the computational expense and improve the efficiency of the design workflow.
An interdisciplinary design framework, where the knowledge of architects, engineers, and computer and robotic scientists is combined, is critical to my doctoral studies. My plan is to develop an automatic algorithm which integrate Computer-aided Design (CAD), the macro models, and open-source computational/structural platforms for Computer-aided Engineering (CAE) analyses and design workflow. The framework aims to develop a dialog between architects and engineers, and links the state of the research to the structural engineering practice. During my academic visit to the research lab of Professor Dr. Henry Burton, my co-supervisor, at the University of California Los Angeles (UCLA), I aim to finalize my research on developing the interactive tool for performance assessment of spatial timber plate systems at the macro scale.
As member of the SBER laboratory at ENAC, I investigate spatial patterns in freshwater benthic biofilm and their interactions with the surrounding hydrodynamics. Stream benthic biofilms are microbial communities that live attached to the stream bed and exposed to the water flow. They develop remarkable morphological features in response to contrasting flow regimes. Biofilms’ architectural attributes relevantly correlate with spatial inhomogeneities in metabolic rates and biodiversity patterns.
For my Mobility project, I have the honor to take part in the prestigious course in Microbial Diversity held in Woods Hole, MA. During this course I will be trained in state-of-the-art techniques to study microbial biodiversity and to characterize metabolic activity. This will provide essential tools to investigate the ecological processes that underly spatial patterns in stream biofims, ultimately linking important ecosystem processes with stream hydrodynamic regimes.
ENAC Doctoral Research Award in the field of environmental engineering for the publication entitled:
“Seascape genomics as a new tool to empower coral reef conservation strategies: An example on north-western Pacific Acropora digitifera.”
The future of coral reefs is under threat since anomalous heat waves are causing the death of reef building corals around the world. Without corals, the entire reef ecosystem is expected to collapse, threatening the survival of up to one third of marine wildlife. Despite the catastrophic perspectives, a glimmer of hope is brought by corals that persist at reefs exposed to recurrent heat waves. Evolutionary adaptation might underpin these observations.
In this publication, we used an approach called seascape genomics to characterize the adaptation to heat stress in a coral population from Japan. We first used remote sensing data to portray patterns of thermal stress across all the reefs of the study area, and then analyzed the genetic variation of corals living across this thermal gradient. We uncovered genetic traits that are more frequent in corals living at reefs exposed to recurrent heat stress. Finally, we predicted the distribution of these adaptive traits for every reef of the study area. This information is of paramount importance, as it constitutes a to-date missing criterion to prioritize reef based on their adaptive potential.
As a postdoctoral fellow at LASIG, I am currently working on extending the seascape genomics approach to other reef systems around the world.